Screening of snake venoms for neurotoxic and myotoxic effects using simple in vitro preparations from rodents and chicks.

Eight snake venoms designated by the WHO as International Reference Venoms, and one additional venom were assessed for neurotoxic and myotoxic effects in vitro using the chick biventer cervicis and the rat and mouse phrenic nerve-diaphragm preparations. The objective was to determine whether any of the preparations could be used to detect evidence of neurotoxic or myotoxic activity prior to a more detailed examination. Bungarus multicinctus venom at concentrations above 1 microgram ml-1 selectively blocked neuromuscular transmission, with no direct effect on muscle fibres. Naja naja kaouthia and Notechis scutatus venoms selectively blocked neuromuscular transmission at low concentrations, but at higher concentrations both venoms caused direct effects on skeletal muscle resulting in contractures, loss of tension following direct stimulation and a loss in sensitivity to elevated [K+]0. Vipera russelli (Thailand) venom also blocked neuromuscular transmission but it was less potent than the venoms of B. multicinctus, N. n. kaouthia and N. scutatus. It also caused contractures in the chick biventer cervicis muscle. The venoms of Echis carinatus (Iran and Mali), Crotalus atrox, Bothrops atrox asper and Trimeresurus flavoviridis had limited neuromuscular blocking activity, and most of these venoms blocked [K+]0 and cholinoceptor stimulation in the chick muscle. Although both chick and rodent muscles allowed the assessment of neurotoxic and myotoxic activity, the chick biventer cervicis was simpler and more robust in use than either of the rodent phrenic nerve-diaphragm preparations. We propose that the chick biventer cervicis muscle could be used as a standard preparation for the screening of snake venoms for neurotoxic and myotoxic effects, and that it may be possible to use this preparation as a means to check that antivenoms can neutralize neurotoxic and direct myotoxic actions of venoms.